Thermostatically-controlled switch



April 28,1931. 7 L. E. TOPHAM 1,802,792

THERMOSTAT'IICALLY CONTROLLED SWITCH Filed Nov. 2, 1926 3 Sheets-Sheet l miness I Fa%vfie nt0r y b 12 H fiuwhe/waf A an 4" Maya April 28, 1931. T-OPHAM 1,802,792

THERMOSTATICALLY CONTROLLED SWITCH Filed Nov. 2, 1926 ,Ei g- 5 ii A 3 Sheets-Sheet 2 April 28, '1931.

L. E. TOPHAM THERMOSTATICALLY CONTROLLED SWITCH Filed Nov. 2, 1926 3 Sheets-Sheet 3 m I E Patented Apr. .28, 1931 UNITED STATS PATENT OFFICE LAURENCE E. TOPHAM, OF WENHAIM, MASSACHUSETTS, ASSIG-NOR TO UNITED SHOE MACHINERY CORPORATION, OF PATERSON, NEW JERSEY, A CORPORATION OF NEW JERSEY THERMOSTI! TICE'; LLY- Application filed November The invention relates to a thermostatically controlled switch for making and breaking an electric circuit and is designed primarily for use in connection with thread waxing devices for applying wax to sewing thread.

The primary object of the present invention is to provide a novel and improved thermostatically controlled switch of this desc -iption which will break the circuit without the sparking and the consequent burning out of the switch contact points which results from inductance in the circuit.

A further object of the invention is to construct a novel and improved thermostatically controlled switch which will act quickly, accurately, and certainly to make or break the circuit as required by the temperature of the melted wax.

With these objects in View the principal feature of the invention consists in the utilization of an alternating current for the heating unit and the provision of mechanism for causing the switch to be opened to break the circuit at that point in the cycle when the current flow is zero.

The several features of the invention con- 'sist also in the devices, combinations and arrangement ofparts herein described and claimed and together with the advantages to be obtained thereby will be easily understood by those skilled in the art from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a side elevation, partly in section, of a wax pot and thermostatically controlled electrical heating units illustrating one embodiment of the present invention and is taken on the line 11 of Fig. 3; Fig. 2 is a diagrammatical view of the electrical circuit including the heating units, the switch, and the motor; Fig. 3 is a plan view looking down on the wax pot; Fig. 4 is a sectional view in elevation taken on the line t4 of Fig. 3; Fig. 5 is a sectional plan view taken on the line 55 of Fig. 1; Fig. 6 is a sectional plan view taken on the line 66 of Fig. 1; Fig. 7 is a detailed plan view of a portion of the parts shown in Fig. 6 with the switch in open position; Fig. 8 is a detailed sectional view in side elevation taken on the line 8-'8 of Fig. 6.

CONTROLLED SWITCH 2, 1926. Serial No. 145,?73.

The preferred embodiment of the invention illustrated in the drawings comprises an electrically heated wax pot adapted for use in shoe sewing machines and provided with thermostatically controlled means for main taining the melted wax at an approximately oven temperature. Two cylindrical heating units connected in parallel in an alternating current circuit are positioned in horizontal pockets on each side of the V shaped lower end of the wax pot to heat the wax. Between the heating units and below the end of the V shaped portion of the wax pot is a thermostat of ordinary construction. A switch controlled by the thermostat is provided for making or breaking the circuit to the heating units. In combination with the thermostat and the switch is a synchronous motor driven by the alternating current which operates positively to open the switch against the pressure of a spring at the zero point of the circuit. As the wax cools the thermostat will operate to trip a latch holding the switch in open position and permit it to close under the influence of its spring.

lcferring more specifically to the drawings a wax pot is indicated at 10 having a V shaped bottom and fastened to a corrospondingly shaped base 12 by the lock bolts 14. The thread is carried across the V shaped bottom of the wax pot entering and leaving through strippers 16. Above the path of the thread is a grate I? spread across the interior of the wax pot and supported on shoulders 18 formed on the sloping walls of the V portion. T n cylindrical heating units 20 are mounted in horizontally placed receptacles in the base 12, one on each side of the V portion of the wax pot in close profs imity to the path of the thread.

A thermostat 22 is mounted between the heating units directly beneath the end of the V portion of the wax pot to control the heating units and maintain the melted wax at an approximately even temperature. t comprises a coiled band of metals such as is commercially prepared for thermal use mounted on a central post and pivotally secured at its outer end at 28 to a horizontal bar 26 which is adapted to move back and forth in a tel lengthwise direction as the band 22 contracts and expands and to swing about its pivot 28 in a horizontal plane. The bar '26 has an arm 29 formed on its mid section which is secured at its free end by a pin and slot connection to the switch arm 30 which is pivotally mounted to swing with the bar 26 in a horizontal plane to open and close the switch. The hub or base of the switch arm 30 is in the form of a yoke 32 which carrles two pivots 34 engaging between them an arm 36 of a fixed bracket- 38. On the outer end of the switch arm 36 is mounted one of the contact points 40, the other being mounted on a fixed bracket 42. The brackets 38 and 42 are mounted on an insulating medium 44 and are equipped with terminal screws for the wiring. The switch arm is normally held with the contact points closed and the arm 26' swung toward the rear by a spring 46 stretched between the arm 26 and a'fiXed bracket 48. A latch 50 is mounted on the bracket 48 and is provided with a ledge 52 adapted to engage a corresponding ledge 54 on the bar 26 to hold the switch in open position against the pressure of thespring 46.

The mechanism for opening the switch comprises a small synchronous motor 56 which is run on the alternating current heating circuit .and carries at one end of the armature shaft 58 a cam disk 60 with a sharply angled cam 62. As the wax pot becomes overheated the thermostat 22 will'tend to uncoil advancing the bar 26 lengthwise to the left into contact with the rapidly turning cam 62. The end of the bar 26 riding on the cam 62 moves forward in a horizontal plane opening the switch very rapidly to its full extent where it is held by the engagement of the ledge 54 with the ledge 52 on the latch 50. Moreover, the cam 62 is so positioned with relation to the operation of the synchronous mot-or that the switch is thrown out at the Zero point in the current. As the wax cools the thermostat will tend to coil up causing the bar 26 to be moved endwise to the right so that the ledge 54 will slide oif from the ledge 52 permitting the bar 26 to swing to the rear under the pressure of its spring 46 to close the switch.

lVith this arrangement which employs sources of power independent of ti e thermostat for opening and closing the switch a particularly sensitive adjustment of the heating units can be maintained for relatively little resistan e is offered by the bar 26 to the adjustment of the thermostat.

For adjustment of the thermostat to determine the temperature at which the wax is to be maintained the post 24 to which the inner end of the band 22 is secured is adj ustably mounted for turning. The post 24 e2;- tends downwardly through a supporting bracket 64 and has at its lower endan enlarged head or nut 66 from which a lever arm 68 extends through an aperture 70 in the base. A collar 72 surrounds the post 24 above the supporting bracket to prevent endwise movement and is secured to the post by means of a set screw. An adjusting screw 74 mounted on a short arm 7 6 formed on the support ing bracket 64to bear against the collar 72 holds the post 24 in the position to which it is turned by the operator by means of the lever arm 68. In order to make the adjusting screw 74 easy of access the screw is provided with a long stem so that the screw head appears on the surface of the base casting in an aperture 7 8 formed in the casting.

As will appear from an inspection of Figs. 1 and 2 the heating units are connected in parallel through the plug to one contact point of the switch the other contact point being connected directly to the other terminal of the plug 80 so that the motor and both heating units are cut off by the opening of the switch.

The operation of the thermostat and the mechanism for making and breaking the heating circuit may be briefly summarized as follows: Starting with the parts in the positions illustrated in Figs. 5 and 6 when the thermostat is tightly coiled with the bar 26 drawn well toward the right and the switch closed the temperature of the melted wax will be gradually increased by the heating units until the thermostat reacting to the increased temperature causes the bar 26 to move to the left into the path of the cam 62 which acts to move the bar 26 forward very rapidly opening the switch and breaking the circuit to the heating units and the motor. The movement of the bar 26 to the left has at the same time brought the ledge 54 on the bar into position to engage the corresponding ledge 52 on the latch 50 to hold the switch in open position against the pressure of the spring 46. The cam is timed with relation to the rotation of the synchronous motor so that the switch is thrown out at the Zero point of the current to prevent sparking and the consequent burning out of the contact points. The melted wax will now be permitted to cool to a point where the thermostat again responds causing the bar 26 to be drawn lengthwise back towards the right disengaging the bar from its latch 50 and allowing the spring 46 to swing the bar and the latch lever towards the rear to close the switch.

The invention having been described, what is claimed is:

l. A thermostatically controlled switch having, in combination, with an alternating current circuit, a thermostat, a switch, a synchronous motor driven by'the alternating current, means controlled by the thermostat and operated by the motor when rendered operative to open the switch, said means being further controlled by the thermostat to close the switch.

2. A thermostatically controlled switch having, in combination, with an alternating currentcircult, a switch, a thermostat, a synchronous motor, and means controlled by the thermostat for causing the motor to open the switch when the value of the current in the circuit is zero, said means being further controlled by the thermostat to close the switch.

3. A thermostatically controlled switch having, in combination, with an alternating current circuit, a switch, a thermostat, a

' synchronous motor, a cam moving in timed relation to the motor, and a member actuated by the thermostat, movable into contact with the cam to open the switch when the value of the current in the circuit is zero and movable in a contrary direction to close the switch.

A thermostatically controlled switch having, in combination, with an alternating current circuit, a movable switch member for making and breaking the circuit, a thermostat, a synchronous motor, connections operating from the motor when thrown into operation by the thermostat to open the switch at the zero point of the current and means controlled by the thermostat to close the switch.

5. A thermostatically controlled switch having, in combination with an alternating current circuit amovable switch contact for making and breaking the circuit, a thermostat, a synchronous motor driven by the alternating current, a cam moving in timed rela tion to the motor, a member controlled by the thermostat movable into the cam path, connections between the member and the switch contact for causing the action of the cam on the said member to open the switch, and a latch for holding the switch in open position which is adapted to permit the switch to close upon the reverse movement of the member.

6. A thermostatically controlled switch having, in combination with an alternating current circuit, a switch for making and breaking the circuit, means for opening the switch at the zero point of the current and for closing the switch, and a thermostat for causing this means to operate to open and close the switch.

7. A thermostatically controlled switch having, in combination, with a circuit, a thermostat, a switch, a motor and means controlled by the thermostat for causing the motor quickly to open the switch to break the circuit and for closing the switch.

8. A thermostatically controlled switch having, in combination, with an alternating current circuit, a switch, a thermostat, a synchronous motor, a cam moving in timed relation to the motor, a member controlled by the thermostat movable into the cam path to open the switch at a predetermined point in the alternating current cycle, and means for holding the switch in open position released by the reverse movement of the member out of the path of the cam.

In testimony whereof I have signed my name to this specification.

LAURENCE E. T'OPHAM. 

